In order to refract light, the common denominator in conventional ophthalmic lenses is the difference in curvature between the front surface and the back surface. However, this poses certain limitations in the design of certain high-end lenses such as prescription sunglasses and progressive lenses. In the case of prescription sunglasses, such design limitations result in prescription sunglasses typically only being available in a limited range of prescriptions. The choice of the curvature of the front surface of the lens (base curve) is determined by the geometry of the frame that wraps around the face. Most prescription sunglasses must, therefore, be made using base curves in the range of six to eight diopters. As a consequence, prescription sunglasses for wearers with a high degree of ametropia would present extremely thick edges in the case of high of myopes, or extremely thick centers in the case of high hyperopes. For this reason, prescription sunglasses are most commonly available for the population whose prescription is in the range of about minus three diopters to plus three diopters.
In the case of multifocal lenses, for example progressive addition lenses, PALs, such design limitations result in only small portions of the progressive addition lens being functional for different lens powers. The geometry of the continuous progressive surface makes it impossible for the lens designer to design lenses with large, wide, and clear regions all at once. Likewise, a design with a larger near region will have a narrower distance region and a design with a shorter corridor to fit a small frame will have more astigmatism, and so on.
Hence, there exists a need for ophthalmic lenses, lens designs, and methods for manufacturing ophthalmic lenses that provide relatively thin prescription clear lenses and sunglasses manufactured for any desired prescription. There also exists a need for ophthalmic lenses, lens designs, and methods for manufacturing ophthalmic lenses that provide for multifocal lenses that have relatively large optically functional portions for the different lens powers.